(a , b , c ) i.p. (4 , 9 , 12)
stiim ca a+b+c = 320
si 4a=9b=12c = k
adica a=k/4 ; b=k/9 si c=k/12
inlocuim in suma data ...
k/4+k/9+k/12 = 320 |*36 (numitorul comun)
9k+4k+3k=11520
16k=11520 => k = 720
=> a=720/4=180;
b=720/9= 80;
c=720/12= 60;
Proba: 180+80+60=320 (A)